Assess Burden of Disease Among Kidney Transplant Recipients With Chronic Active Antibody Mediated Rejection

Inclusion Criteria: Chronic Active AMR group: * 18 Years and older * Recipient of blood group system (ABO) compatible solitary kidney transplant between \[1Jan2013\] and \[1Jan2018\] * Chronic active AMR diagnosed via kidney biopsy based upon Banff criteria. Patients who additionally have diagnoses such as TCMR, acute tubular necrosis, recurrence of primary kidney disease are also eligible if not the predominant pathology. * DSA antibodies within prior 6 months of the biopsy which confirmed chronic active AMR * Minimum of 3 years of follow up data following diagnosis of chronic active AMR (unless patient had died) * eGFR at time of diagnosis of chronic active AMR of \>25ml/min/1.73m2 Non-Chronic active AMR group: * Age 18 years or older * Recipient of ABO compatible solitary kidney transplant between \[1 Jan 2013\] and \[1Jan2018\] * No documented diagnosis of chronic active AMR during the data extraction period. Patients with other diagnoses such as TCMR, acute tubular necrosis, recurrence of primary kidney disease are also eligible. Patients may or may not have had biopsies. * Minimum of 4 years of follow up data since transplant (unless patient has died) * eGFR of \>25ml/min/1.73m2 at time of matching Exclusion Criteria: Chronic active AMR group: * Recipient of a multi-organ transplant * ABO-incompatible transplant * Patient lost to follow up within the first 3 years post-diagnosis of chronic active AMR and whose allograft status (graft failure or patient death) is unknown. Non-Chronic active AMR group: * Recipient of a multi-organ transplant * ABO-incompatible transplant * Patient lost to follow up within the first 4 years of transplant and whose allograft status (graft failure or patient death) is unknown.